1. Field of the Invention
This invention relates generally to pipeline closures, and particularly to clamp-type closures that are designed for pigging subsea petroleum pipelines.
2. Description of the Prior Art
Petroleum products flowing through pipelines deposit silt, mud, and foreign material on the walls of the pipe, much like fatty deposits within arteries. Debris traveling through oil pipelines has a tendency to accumulate on the pipe wall, which accordingly reduces the flow area and efficiency of the pipeline. Further, water and other liquids settle in low points of gas pipelines, forming similar obstructions to the flow of fluid through the line. To clean, or flush-out, the pipeline it is common practice within the petroleum industry to insert a xe2x80x9cpigxe2x80x9d into the pipeline. For example, U.S. Pat. Nos. 3,125,116; 3,218,660; 3,246,355; and 3,473,550, disclose various devices for launching and receiving pigs in pipelines. The pig may be moved through the pipeline to push any foreign debris that may be obstructing the flow through the line. This foreign material is either removed at the end of the pipeline, or ejected somewhere along the path of the pipeline.
To obtain access to pipeline, a closure device may be used at an opening of the pipeline. Referring to FIGS. 1A-1B, a standard closure device 10 according to the prior art is illustrated. The standard closure device 10 includes a door 12, a clamp 20, and a mounting hub 30. In FIG. 1A, a frontal view shows the door 12 pivoted adjacent the open clamp 20. In FIG. 1B, a side view shows the closure device 10 in a locked down or closed position by solid line and in an open position by dotted line. The door 12 includes a blind hub 14 with a flange 16. The door 12 attaches to the clamp 20 by a hinge 18. The clamp 20 includes first and second clamp segments 22a and 22b, which are locked or retracted with a plurality of threaded rods 24 and nuts 26. The clamp segments 22a and 22b are supported on slide rods 28a and 28b. The mounting hub 30 includes a flange 32 and an opening 34. The opening 34 provides access to a pipeline (not shown). In the closed position shown in FIG. 1A, the flange 16 of the blind 14 and the flange 32 of the mounting hub 30 are held together within grooves 23 in the locked clamp segments 22a and 22b. 
To open the standard closure 10, the nuts 28 are loosened to retract the clamp segments 22a and 22b from one another. The hinged door 12 is pivoted to move the blind hub 14 away from the mounting hub 30 and to provide fast, easy access to the opening 32. A safety interlock system (not shown) may prevent opening when the closure 10 is pressurized. Only one operator is required for a quick open/close. The standard closure device 10 utilizes a high-pressure metal-to-metal seal to provide a positive, leak proof seal in applications such as pig launchers and receivers, filters, strainers, reactors, or pressure vessels.
In many adverse environments and/or locations, such as flow lines at subsea oil or gas wellheads, pigging a line may expose divers to extreme danger, that is of course if the depth even allows a diver to be present. The expense and the inherent dangers to life that are associated with diver-assisted pipeline operations prevent many subsea pipelines from being flushed and cleaned. The current invention is directed to a remotely operated closure device.
One aspect of the present invention provides a closure device. The closure device includes a first mechanism moving a first hub into relation with a second hub attached to a conduit to close access to the conduit or moving the first hub out of relation with the second hub to open access to the conduit. The closure device includes a second mechanism retaining the first hub in sealed engagement with the second hub or releasing the first hub from sealed engagement with the second hub. The closure device includes a third mechanism simultaneously actuating the first mechanism and the second mechanism.
Another aspect of the present invention provides a remotely operable closure, including a base hub, a clamping mechanism, a drive mechanism, and a closure mechanism. The base hub allows access to a conduit. The clamping mechanism is disposed about the base hub and is actuatable to clamp or unclamp about the base hub and a blind hub. The drive mechanism is remotely operable to actuate the clamping mechanism. the closure mechanism is actuatable with the clamping mechanism to move the blind hub into or out of engagement with the base hub.
Yet another aspect of the present invention provides a method for remotely operating a closure. The method includes the steps of: actuating a single mechanism with a first operation; moving a first hub into relation with a second hub to close access to the closure with the first operation; clamping the first hub in sealed engagement with the second hub with the first operation; actuating the single mechanism with a second operation; unclamping the first hub from sealed engagement with the second hub with the second operation; and moving the first hub out of relation with the second hub to open access to the closure with the second operation.
The foregoing summary is not intended to summarize each potential embodiment of every aspect of the invention disclosed herein, but merely to summarize the appended claims.